It frequently is necessary to prevent fish from passing up a stream or canal but at the same time not impede the flow of the stream or prevent solid objects from moving downstream. For example, it is common practice for industrial plants to use water from streams as cooling water in their heat exchangers. The water is drawn from the stream, is passed through the heat exchanger and is discharged downstream of the inlet. School fish, such as menhaden, will follow the warm discharge from the heat exchanger up the stream and if they are not stopped will clog the heat exchanger outlet. A net or screen placed across the stream is not a practical solution to the problem because debris and trash can not pass through such a barrier and the barrier will soon become clogged to the point where the stream will be effectively dammed and will overflow the barrier or the force and weight of the water will tear the barrier out. Previous attempts to solve this problem have involved moving screens in the form of moving belts or panels which pass the trash and debris around the end of the barrier. Such devices are expensive, require considerable maintenance and are often unable to pass large objects such as barrels, tree trunks, and the like.